Thermal energy storage and cooling system with enhanced heat exchange capability

ABSTRACT

Disclosed is a method and device to increase the cooling load that can be provided by a refrigerant-based thermal energy storage and cooling system with an improved arrangement of heat exchangers. This load increase is accomplished by circulating cold water surrounding a block of ice, used as the thermal energy storage medium, through a secondary heat exchanger where it condenses refrigerant vapor returning from a load. The refrigerant is then circulated through a primary heat exchanger within the block of ice where it is further cooled and condensed. This system is known as an internal/external melt system because the thermal energy, stored in the form of ice, is melted internally by a primary heat exchanger and externally by circulating cold water from the periphery of the block through a secondary heat exchanger.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/366,784, filed on Feb. 6, 2009. This application is a divisional ofU.S. patent application Ser. No. 11/138,762, filed on May 25, 2005, andpatented as U.S. Pat. No. 7,503,185 on Mar. 17, 2009. This applicationis based upon and claims the benefit of U.S. provisional application No.60/574,449, entitled “Refrigerant-Based Energy Storage and CoolingSystem with Enhanced Heat Exchange Capability”, filed May 25, 2004, theentire disclosure of which is hereby specifically incorporated byreference for all that it discloses and teaches.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to systems providing storedthermal energy in the form of ice, and more specifically to ice storagecooling and refrigeration systems.

2. Description of the Background

With the increasing demands on peak demand power consumption, icestorage has been utilized to shift air conditioning power loads tooff-peak times and rates. A need exists not only for load shifting frompeak to off-peak periods, but also for increases in air conditioningunit capacity and efficiency. Current air conditioning units havingenergy storage systems have had limited success due to severaldeficiencies including reliance on water chillers that are practicalonly in large commercial buildings and have difficulty achievinghigh-efficiency. In order to commercialize advantages of thermal energystorage in large and small commercial buildings, thermal energy storagesystems must have minimal manufacturing costs, maintain maximumefficiency under varying operating conditions, emanate simplicity in therefrigerant management design, and maintain flexibility in multiplerefrigeration or air conditioning applications.

Systems for providing thermal stored energy have been previouslycontemplated in U.S. Pat. No. 4,735,064, U.S. Pat. No. 4,916,916, bothissued to Harry Fischer, U.S. Pat. No. 5,647,225 issued to Fischer etal, and U.S. patent application Ser. No. 10/967,114 filled Oct. 15, 2004by Narayanamurthy et al. All of these patents utilize ice storage toshift air conditioning loads from peak to off-peak electric rates toprovide economic justification and are hereby incorporated by referenceherein for all they teach and disclose.

SUMMARY OF THE INVENTION

An embodiment of the present invention may comprise a refrigerant-basedthermal energy storage and cooling system comprising: a condensing unit,the condensing unit comprising a compressor and a condenser; arefrigerant management unit connected to the condensing unit, therefrigerant management unit that regulates, accumulates and pumpsrefrigerant; a load heat exchanger connected to the refrigerantmanagement unit that provides cooling to a cooling load by increasingthe enthalpy of the refrigerant; a tank filled with a fluid capable of aphase change between liquid and solid and containing a primary heatexchanger therein, the primary heat exchanger being connected to therefrigerant management unit that uses the refrigerant from therefrigerant management unit to cool the fluid and to freeze at least aportion of the fluid within the tank; and, a secondary heat exchangerconnected to the load heat exchanger that facilitates thermal contactbetween the cooled fluid and the refrigerant thereby reducing theenthalpy of the refrigerant, and returns the warmed fluid to the tank.

An embodiment of the present invention may also comprise a method ofproviding load cooling with a refrigerant-based thermal energy storageand cooling system comprising the steps of: condensing a first expandedrefrigerant with a condensing unit to create a first condensedrefrigerant; supplying the first condensed refrigerant to an evaporatingunit constrained within a tank filled with a fluid capable of a phasechange between liquid and solid; expanding the first condensedrefrigerant during a first time period within the evaporating unit tofreeze a portion of the fluid within the tank and create a cooled fluid,a frozen fluid and a second expanded refrigerant; circulating at least aportion of the cooled fluid through a secondary heat exchanger in asecond time period to reduce the enthalpy of the second expandedrefrigerant and create a lower enthalpy refrigerant; circulating thelower enthalpy refrigerant through the evaporating unit within thefrozen fluid to condense the lower enthalpy refrigerant and create asecond condensed refrigerant; and, expanding the second condensedrefrigerant to provide the load cooling.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 illustrates an embodiment of a refrigerant-based thermal energystorage and cooling system with enhanced heat exchange capability.

FIG. 2 illustrates an embodiment of a refrigerant-based thermal energystorage and cooling system with enhanced heat exchange capability.

FIG. 3 illustrates an embodiment of a refrigerant-based thermal energystorage and cooling system with multiple enhanced heat exchangers.

FIG. 4 illustrates an embodiment of a refrigerant-based thermal energystorage and cooling system with enhanced heat exchange capabilityutilizing a shared fluid bath.

FIG. 5 illustrates an embodiment of a refrigerant-based thermal energystorage and cooling system with enhanced heat exchange capabilityutilizing a shared fluid bath.

DETAILED DESCRIPTION OF THE INVENTION

While this invention is susceptible to embodiment in many differentforms, there is shown in the drawings and will be described herein indetail specific embodiments thereof with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the invention and is not to be limited to the specificembodiments described.

As shown in FIG. 1, an embodiment of a refrigerant-based thermal energystorage and cooling system is depicted comprising the five majorcomponents that define the system. The air conditioner unit 102 utilizesa compressor 110 and a condenser 111 to produce high-pressure liquidrefrigerant delivered through a high-pressure liquid supply line 112 tothe refrigeration management unit 104. The refrigeration management unit104 is connected to a thermal energy storage unit 106 comprising aninsulated tank 140 filled with fluid (e.g. water) and ice-making coils142. The air conditioner unit 102, the refrigeration management unit 104and the thermal energy storage unit 106 act in concert to provideefficient multi-mode cooling to the load unit 108 comprising a load heatexchanger 108 (indoor cooling coil assembly) and thereby perform thefunctions of the principal modes of operation of the system. Acirculation loop to a secondary heat exchanger 162 acts to circulate anddestratify fluid 152 within the insulated tank 140 and draw heat fromrefrigerant leaving the load heat exchanger 123.

As further illustrated in FIG. 1, during one time period (ice building)the air conditioner unit 102 produces high-pressure liquid refrigerantdelivered through a high-pressure liquid supply line 112 to therefrigeration management unit 104. The high-pressure liquid supply line112 passes through an oil still/surge vessel 116 forming a heatexchanger therein. The oil still/surge vessel 116 serves a trilogy ofpurposes: it is used to concentrate the oil in the low-pressurerefrigerant to be returned to the compressor 110 through the oil returncapillary 148 and dry suction return 114; it is used to store liquidrefrigerant during the second time period (cooling mode); and, it isused to prevent a liquid floodback to compressor 110 immediatelyfollowing compressor 110 startup due to a rapid swelling of refrigerantwithin the ice freezing/discharge coils 142 and the universalrefrigerant management vessel 146. Without the oil still/surge vessel116, oil would remain in the system and not return to the compressor110, ultimately causing the compressor 110 to seize due to lack of oil,and the heat exchangers also become less effective due to fouling.Without the oil still/surge vessel 116, it may not be possible toadequately drain liquid refrigerant from the ice freezing/dischargecoils during the second time period (cooling mode) in order to utilizenearly the entire heat transfer surface inside the icefreezing/discharge coils 142 for condensing the refrigerant vaporreturning from the load heat exchanger 123.

Cold liquid refrigerant comes into contact with an internal heatexchanger that is inside of oil still/surge vessel 116, a high-pressure(warm) liquid resides inside of the internal heat exchanger. A vaporforms which rises to the top of the still/surge vessel 116 and passesout vent capillary 128 (or an orifice), to be re-introduced into the wetsuction return 124. The length and internal diameter of the ventcapillary 128 limits the pressure in the oil still/surge vessel 116 andthe mass quantity of refrigerant inside the oil still/surge vessel 116during an ice building time period.

When activated during a second time period, a liquid refrigerant pump120 supplies the pumped liquid supply line 122 with refrigerant liquidwhich then travels to the evaporator coils of the load heat exchanger123 within the load unit 108 of the thermal energy storage and coolingsystem. Low-pressure refrigerant returns from the evaporator coils ofthe load heat exchanger 123 via wet suction return 124 to an accumulatoror universal refrigerant management vessel (URMV) 146. Simultaneously,the partially distilled oil enriched refrigerant flows out the bottom ofthe oil still/surge vessel 116 through an oil return capillary 148 andis re-introduced into the dry suction return 114 with the low-pressurevapor exiting the universal refrigerant management vessel 146 andreturns to the air conditioner unit 102. The oil return capillary 148controls the rate at which oil-rich refrigerant exits the oilstill/surge vessel 116. The oil return capillary, which is also heatedby the warm high-pressure liquid refrigerant inside the high-pressureliquid supply line 112, permits the return of oil to the oil sump insidecompressor 110.

Additionally, the wet suction return 124 connects with the upper headerassembly 154 that connects with bifurcator 130 to supply low-pressurerefrigerant to the system from the mixed-phase regulator 132. Themixed-phase regulator 132 meters the flow of refrigerant within thesystem by incorporating a valve (orifice) that pulses open to releaseliquid-phase refrigerant, only when there is sufficient quantity ofliquid within the condenser 111. This mixed-phase regulator 132 reducessuperfluous vapor feed (other than flash gas which forms when thepressure of saturated high-pressure liquid decreases) to the universalrefrigerant management vessel 146 from the compressor 110, while alsodropping the required pressure from the condenser pressure to theevaporator saturation pressure. This results in greater overallefficiency of the system while simplifying the refrigerant managementportion 104 of the gravity recirculated or liquid overfeed system. It istherefore beneficial to have a regulated flow controller that canregulate the pressure output, or meter the flow of the refrigerant, bycontrolling the flow independently of temperature and vapor content ofthe refrigerant. This pressure, or flow control, is performed withoutseparate feedback from other parts of the system, such as is performedwith conventional thermal expansion valves.

The insulated tank 140 contains dual-purpose ice freezing/dischargecoils 142 arranged for gravity recirculation and drainage of liquidrefrigerant and are connected to an upper header assembly 154 at thetop, and to a lower header assembly 156 at the bottom. The upper headerassembly 154 and the lower header assembly 156 extend outward throughthe insulated tank 140 to the refrigeration management unit 104. Whenrefrigerant flows through the ice freezing/discharging coils 142 andheader assemblies 154 and 156, the coils act as an evaporator while thefluid/ice 152 (phase change material) solidifies in the insulated tank140 during one time period. The ice freezing/discharging coils 142 andheader assemblies 154 and 156 are connected to the low-pressure side ofthe refrigerant circuitry and are arranged for gravity or pumpedrecirculation and drainage of liquid refrigerant. During a second timeperiod, warm vapor-phase refrigerant circulates through the icefreezing/discharging coils 142 and header assemblies 154 and 156 andcondenses the refrigerant, while melting the ice.

As heat is transferred from the ice freezing/discharging coils 142 tothe surrounding ice, a layer of water forms around the annulus of theindividual coils 142. Once this layer of water forms a sufficientenvelope around a coil, it begins to act as an insulator between the icefreezing/discharging coils 142 and the ice block. This condition willpersist until such a time when the water annulus becomes large enoughfor considerable water circulation to overcome this localized thermalstratification. In order to compensate for the inability of the systemto produce high levels of instantaneous cooling load, the outer surfaceof the ice block is additionally utilized.

Within the insulated tank 140, the entirety of the water is not frozenduring the ice build cycle, and therefore, an amount of watercontinuously surrounds the block of ice. At the bottom of the tank, thiswater is very near the freezing point (approximately 33-34° F.), and isdrawn into cold water inlet line 166 by a water pump 164 and fed to asecondary heat exchanger 162. Refrigerant, returning from the load heatexchanger 122 (usually an evaporator coil in a cooling duct) is divertedfrom its normal path of the wet suction return 124 and fed to thesecondary heat exchanger 162 via secondary cooling line 170. Here, thewarm refrigerant is cooled by water entering from cold water inlet line166 and condenses, increasing the proportion of liquid in therefrigerant which is then fed through a secondary cooling outlet line172 to the primary heat exchanger 160. The header configuration drivesmost of the liquid to the universal refrigerant management vessel 146and the vapor to the primary heat exchanger 160. This remainingrefrigerant vapor is then condensed within the primary heat exchanger160 in the insulated tank 140. After transferring heat to therefrigerant in the secondary heat exchanger 162, the warmed water isreturned to any portion (upper portion depicted) of the insulated tank140 via warm water return line 168.

The refrigerant management unit 104 includes the universal refrigerantmanagement vessel 146 which functions as an accumulator. The universalrefrigerant management vessel 146 is located on the low-pressure side ofthe refrigerant circuitry and performs several functions. The universalrefrigerant management vessel 146 separates the liquid-phase from thevapor-phase refrigerant during the refrigerant energy storage period andagain during the cooling period. The universal refrigerant managementvessel 146 also provides a static column of liquid refrigerant duringthe refrigerant energy storage period that sustains gravity circulationthrough the ice freezing/discharge coils 142 inside the insulated tank140. The dry suction return 114 provides low-pressure vapor-phaserefrigerant to compressor 110, within the air conditioner unit 102,during a first thermal energy storage time period from an outlet at thetop of the universal refrigerant management vessel 146. A wet suctionreturn 124 is provided through an inlet in the top of the upper headerassembly 154 for connection to an evaporator (load heat exchanger 123)during the second time period when the refrigerant energy storage systemprovides cooling.

The first time period is the refrigerant energy storage time period inwhich sensible heat and latent heat are removed from water causing thewater to freeze. The output of the compressor 110 is high-pressurerefrigerant vapor that is condensed to form high-pressure liquid. Avalve (not shown) on the outlet of the liquid refrigerant pump 120 (inthe pumped liquid supply line 122) controls the connection to the loadunit 108, for example closing the connection when the liquid refrigerantpump is stopped.

During the first time period, heat flows from high-pressure warm liquidto the low-pressure cold liquid inside the oil still/surge vessel 116which boils the cold liquid. The pressure rise resulting from the vaporthat forms during liquid boiling inside the oil still/surge vessel 116causes the cold liquid to exit the oil still/surge vessel 116 and movesit to the ice freezing/discharge coils 142 where it is needed for propersystem operation during the first time period. During the second timeperiod, warm high-pressure liquid no longer flows through thehigh-pressure liquid supply line 112 because the compressor 110 insideair conditioner unit 102 is off. Therefore, the aforementioned heat flowfrom warm liquid to cold liquid ceases. This cessation permits liquidfrom the universal refrigerant management vessel 146 and icefreezing/discharge coils to flow back into the oil still/surge vessel116 because the high internal vessel gas pressure during the first timeperiod no longer exists.

During the thermal energy storage period, high-pressure liquidrefrigerant flows from the air conditioner unit 102 to an internal heatexchanger, which keeps all but a small amount of low-pressure liquidrefrigerant out of the oil still/surge vessel 116. The refrigerant thatis inside the vessel boils at a rate determined by two capillary tubes(pipes). One capillary is the vent capillary 128 that controls the levelof refrigerant in the oil still/surge vessel 116. The second, the oilreturn capillary 148, returns oil-enriched refrigerant to the compressor110 within the air conditioner unit 102 at a determined rate. The columnof liquid refrigerant in the universal refrigerant management vessel 146is acted on by gravity and positioning the oil still/surge vessel 116near the bottom of the universal refrigerant management vessel 146column maintains a steady flow of supply liquid refrigerant to the oilstill/surge vessel 116 and into the thermal energy storage unit 106. Thesurge function allows excess refrigerant during the cooling period to bedrained from the ice freezing/discharging coils 142 that are in theinsulated tank 140, keeping the surface area maximized for condensingrefrigerant during the second time period.

The physical positioning of the oil still/surge vessel 116, in referenceto the rest of the system, is a performance factor as an oil still andas a surge vessel. This oil still/surge vessel 116 additionally providesthe path for return of the oil that migrates with the refrigerant thatmust return to the compressor 110. The slightly subcooled (cooler thanthe vapor-to-liquid phase temperature of the refrigerant) high-pressureliquid refrigerant that exits the oil still/surge vessel 116 flowsthrough a mixed-phase regulator 132 during which a pressure drop occurs.

As stated above, the refrigerant management unit 104 receiveshigh-pressure liquid refrigerant from the air conditioner unit 102 via ahigh-pressure liquid supply line 112. The high-pressure liquidrefrigerant flows through the heat exchanger within the oil still/surgevessel 116, where it is slightly subcooled, and then flows to themixed-phase regulator 132, where the refrigerant pressure drop takesplace. The use of a mixed-phase regulator 132 provides many favorablefunctions besides liquid refrigerant pressure drop. The mass quantity ofrefrigerant that passes through the mixed-phase regulator 132 matchesthe refrigerant boiling rate inside the ice making coils 142 during thethermal energy storage time period, thereby, eliminating the need for arefrigerant level control.

The mixed-phase regulator 132 passes liquid refrigerant, but closes whensensing vapor. The existence of vapor on the low side of the regulatorcreates pressure to close the valve which combines with the other forcesacting upon the piston, to close the piston at a predetermined triggerpoint that corresponds to desired vapor content. This trigger point maybe predetermined by regulator design (e.g., changing the geometry of theregulator components as well as the materials). The trigger point mayalso be adjusted by automatic or manual adjustments to the regulatorgeometry (e.g., threaded adjustment to the piston displacement limits).

The pulsing action created in the refrigerant exiting the mixed-phaseregulator 132 as a result of the opening and closing of the mixed-phaseregulator 132 creates a pulsing effect upon the liquid refrigerant thatcreates a pressure wave within the closed column in the universalrefrigerant management vessel 146. This agitates the liquid refrigerantin both the ice making coils 142 and the condenser 111 during thethermal energy storage first time period, and enhances heat transfer aswell as assists in segregating liquid and vapor-phase refrigerant. Themixed-phase regulator 132, in conjunction with the universal refrigerantmanagement vessel 146, also drains the air conditioner unit 102 ofliquid refrigerant during the first time period keeping its condensingsurface area free of liquid condensate and therefore available forcondensing. The mixed-phase regulator 132 allows head pressure of theair-cooled air conditioner unit 102 to float with ambient temperature.The system does not require a superheat circuit, which is necessary withmost condensing units connected to a direct expansion refrigerationdevice.

The low-pressure mixed-phase refrigerant that leaves the mixed-phaseregulator 132 passes through a bifurcator 130 to an eductor (or injectornozzle), located between the inlet, to the universal refrigerantmanagement vessel 146 and the upper header assembly 154 of the icemaking coils 142, to assist with gravity refrigerant circulation. Duringthe refrigerant thermal energy storage time period, the eductor createsa drop in pressure immediately upstream from the eductor, and in theupper header assembly 154 of the thermal energy storage unit 106, as therefrigerant leaves the bifurcator 130, thereby increasing the rate ofrefrigerant circulation in the ice making coils 142 while simultaneouslyimproving system performance.

The mixed-phase regulator 132 also reacts to changes in refrigerant massflow from compressor 110 as the pressure difference across its outletport varies with increasing or decreasing outdoor ambient airtemperatures. This allows the condensing pressure to float with theambient air temperature. As the ambient air temperature decreases, thehead pressure at the compressor 110 decreases which reduces energyconsumption and increases compressor 110 capacity. The mixed-phaseregulator 132 allows liquid refrigerant to pass while closing a pistonupon sensing vapor. Therefore, the mixed-phase regulator 132 temporarilyholds the vapor-phase mixture in a “trap”. Upon sensing high-pressureliquid, the piston lifts from its seat which allows liquid to pass.

The mixed-phase regulator 132 therefore, allows vapor pressure toconvert high-pressure liquid refrigerant to low-pressure liquidrefrigerant and flash vapor. The vapor held back by the mixed-phaseregulator 132 increases the line pressure back to the condenser 111 andis further condensed into a liquid. The mixed-phase regulator 132 isself regulating and has no parasitic losses. Additionally, themixed-phase regulator 132 improves the efficiency of the heat transferin the coils of the heat exchangers by removing vapor out of the liquidand creating a pulsing action on both the low-pressure and high-pressuresides of the system. As stated above, the mixed-phase regulator opens tolet low-pressure liquid through and then closes to trap vapor on thehigh-pressure side and creates a pulsing action on the low-pressure sideof the regulator. This pulsing action wets more of the inside wall ofthe heat exchanger at the boiling and condensing level, which aids inthe heat transfer.

The low-pressure mixed-phase refrigerant enters the universalrefrigerant management vessel 146 and the liquid and vapor componentsare separated by gravity with liquid falling to the bottom and vaporrising to the top. The liquid component fills the universal refrigerantmanagement vessel 146 to a level determined by the mass charge ofrefrigerant in the system, while the vapor component is returned to thecompressor of the air conditioner unit 102. In a normal direct expansioncooling system, the vapor component circulates throughout the systemreducing efficiency. With the embodiment depicted in FIG. 1, the vaporcomponent is returned to the compressor 110 directly without having topass though the evaporator. The column of liquid refrigerant in theuniversal refrigerant management vessel 146 is acted upon by gravity andhas two paths during the thermal energy storage time period. One path isto the oil still/surge vessel 116 where the rate is metered by capillarytubes 128 and 148.

The second path for the column of liquid refrigerant is to the lowerheader assembly 156, through the ice freezing/discharge coils 142 andthe upper header assembly 154, and back to the compressor 110 throughthe universal refrigerant management vessel 146. This gravity assistedcirculation stores thermal capacity in the form of ice when the tank isfilled with a phase-change fluid such as water. The liquid static headin the universal refrigerant management vessel 146 acts as a pump tocreate a flow within the ice freezing/discharge coils 142. As therefrigerant becomes a vapor, the level of liquid in the coil is forcedlower than the level of the liquid in the universal refrigerantmanagement vessel 146, and therefore, promotes a continuous flow betweenthe universal refrigerant management vessel 146 through icefreezing/discharge coils 142. This differential pressure between theuniversal refrigerant management vessel 146 and the icefreezing/discharge coils 142 maintains the gravity circulation.Initially vapor only, and later (in the storage cycle), both refrigerantliquid and vapor, are returned to the universal refrigerant managementvessel 146 from the upper header assembly 154.

As refrigerant is returned to the universal refrigerant managementvessel 146 the heat flux gradually diminishes due to increasing icethickness (increasing thermal resistance). The liquid returns to theuniversal refrigerant management vessel 146 within the refrigerantmanagement unit 104 and the vapor returns to the compressor 110 withinthe air conditioner unit 102. Gravity circulation assures uniformbuilding of the ice. As one of the ice freezing/discharge coils 142builds more ice, its heat flux rate is reduced. The coil next to it nowreceives more refrigerant until all coils have a nearly equal heat fluxrate.

The design of the ice freezing/discharge coils 142 creates an ice buildpattern that maintains a high compressor suction pressure (therefore anincreased suction gas density) during the ice build storage (first) timeperiod. During the final phase of the thermal energy storage (first)time period, all remaining interstices between each icefreezing/discharge coil 142 become closed with ice, therefore theremaining water to ice surface area decreases, and the suction pressuredrops dramatically. This drop on suction pressure can be used as a fullcharge indication that automatically shuts off the condensing unit withan adjustable refrigerant pressure switch.

When the air conditioner unit 102 turns on during the thermal energystorage first time period, low-pressure liquid refrigerant is preventedfrom passing through the liquid refrigerant pump 120 by gravity, andfrom entering the load heat exchanger 123 by a poppet valve (not shown)in the pumped liquid supply line 122. When the thermal energy storagesystem is fully charged, and the air conditioning unit 102 shuts off,the mixed-phase regulator 132 allows the refrigerant system pressures toequalize quickly. This rapid pressure equalization permits use of a highefficiency, low starting torque motor in the compressor 110. The loadheat exchanger 123 is located either above or below the thermal energystorage unit 106 so that refrigerant may flow from the load heatexchanger 123 (as mixed-phase liquid and vapor), or through the wetsuction return 124 (as vapor only at saturation), to the upper headerassembly 154. After passing through the upper header assembly 154 itthen passes into the ice freezing/discharge coils for condensing back toa liquid.

As shown in FIG. 1, an embodiment of a high efficiency refrigerantenergy storage and cooling system is depicted comprising the five majorcomponents that define the system. The air conditioner unit 102 is aconventional condensing unit that utilizes a compressor 110 and acondenser 111 to produce high-pressure liquid refrigerant deliveredthrough a high-pressure liquid supply line 112 to the refrigerationmanagement unit 104. The refrigeration management unit 104 is connectedto a thermal energy storage unit 106 comprising an insulated tank 140filled with water and ice-making coils 142. Finally, a secondary heatexchanger unit 162 introduces external melt capability providingadditional instantaneous cooling load to the system. The air conditionerunit 102, the refrigeration management unit 104 and the thermal energystorage unit 106 act in concert to provide efficient multi-mode coolingto the load heat exchanger 108 (indoor cooling coil assembly) andthereby perform the functions of the principal modes of operation of thesystem. The circulation loop created with the secondary heat exchanger162 transfers heat between the refrigerant leaving the load heatexchanger 123 and the fluid within the insulated tank 140. This loopacts to circulate and destratify fluid 152 within the insulated tank 140and draw heat from refrigerant leaving the load heat exchanger 123. Thissecondary heat exchanger loop can be switched in and out of the systemby valves 188 as necessary when instantaneous cooling load is needed.The system shown is known as an internal/external melt system becausethe thermal energy that has been stored in the form of ice is meltedinternally to the block by freezing/discharging coils 142 and externallyby circulating cold water from the periphery of the block through asecondary heat exchanger 162. This secondary heat exchanger loop can beswitched in and out of the system by valves 188 as necessary wheninstantaneous cooling load is needed.

FIG. 2 illustrates an embodiment of a refrigerant-based thermal energystorage cooling system with enhanced heat exchange capability. A thermalenergy storage and cooling system with a conventional condensing unit202 (air conditioner) utilizes a compressor and condenser to producehigh-pressure liquid refrigerant delivered through a high-pressureliquid supply line 212 to the refrigeration management and distributionsystem 204 which can include a universal refrigerant management vessel246 and a liquid refrigerant pump 220. The universal refrigerantmanagement vessel 246 receives the low-pressure mixed phase 262 liquidrefrigerant that has been dropped in pressure from the high-pressureliquid supply line 212. Refrigerant is accumulated in a universalrefrigerant management vessel 246 that separates the liquid-phaserefrigerant from the vapor-phase refrigerant. A mixed-phase regulator(not shown) can be used to minimize vapor feed to the universalrefrigerant management vessel 246 from the compressor, while decreasingthe refrigerant pressure difference from the condenser to the evaporatorsaturation pressure.

In thermal energy storage mode, the universal refrigerant managementvessel 246 feeds liquid refrigerant through liquid feed line 266 to theprimary heat exchanger 260 that stores the cooling (thermal energy) inthe form of ice or an ice block 242. Upon delivering the cooling to theprimary heat exchanger 260, mixed-phase refrigerant is returned to theuniversal refrigerant management vessel 246 via a wet suction returnline 224. Dry suction return line 218 returns vapor phase refrigerant tobe compressed and condensed in the condensing unit 202 to complete thethermal energy storage cycle.

In cooling mode, the universal refrigerant management vessel 246 feedsliquid refrigerant through pump inlet line 264 to a liquid refrigerantpump 220 which then pumps the refrigerant to an evaporator coil 222 viapump outlet line 260. Upon delivering the cooling to the evaporator coil222, mixed-phase or saturated refrigerant is returned to the primaryheat exchanger 260 via a low-pressure vapor line 268 and is condensedand cooled utilizing an ice block 242 that is made during thermal energystorage mode. The vapor-phase refrigerant is then returned to theuniversal refrigerant management vessel 246 via liquid feed line 266. Asecondary heat exchanger unit 270 introduces an external melt to thesystem to provide additional instantaneous cooling load to the system.By providing a system with internal/external melt capability, thermalenergy stored in the form of an ice block 242 is melted internally byfreezing/discharging coils within the primary heat exchanger 260 andexternally by circulating cold water from the periphery of the blockthrough the secondary heat exchanger 270. This allows the system torealize as much as a fourfold increase in instantaneous coolingcapacity.

During this second time period (cooling mode), warm vapor phaserefrigerant circulates through ice freezing/discharging coils within theprimary heat exchanger 260 and melts the ice block 242 from the insideout, providing a refrigerant condensing function. As heat is transferredfrom these ice freezing/discharging coils to the surrounding ice block242, a layer of water forms around the annulus of the individual coils.As described above, once this layer of water forms a sufficient envelopearound a coil, it begins to act as an insulator between the icefreezing/discharging coils and the ice block 242. This condition willpersist until such a time when the water annulus becomes large enoughfor considerable water circulation to overcome this localized thermalstratification. In order to compensate for the inability of the systemto produce high levels of instantaneous cooling load, the outer surfaceof the ice block is additionally utilized.

Within the insulated tank 240, the entirety of the water is not frozenduring the ice build cycle, and therefore, an amount of watercontinuously surrounds the block of ice. At the bottom of the insulatedtank 240, this water is very near the freezing point (approximately33-34° F.), and is drawn into cold water line 274 by a water pump 272and fed to the secondary heat exchanger 270. Refrigerant, returning fromthe evaporator coil 222 can be diverted from its normal path of the wetsuction return 224 and fed to the secondary heat exchanger 270 viasecondary cooling inlet line 278. Here, the warm refrigerant is cooledby water entering from cold water line 274 and condenses, increasing theproportion of liquid in the refrigerant which is then fed through asecondary cooling outlet line 280 to the primary heat exchanger 260where the header configuration drives most of the liquid to theuniversal refrigerant management vessel 246 and the vapor to the primaryheat exchanger 260. This remaining refrigerant vapor is then condensedwithin the primary heat exchanger 260 in the insulated tank 240. Aftertransferring heat to the refrigerant in the secondary heat exchanger270, the warmed water is returned to the upper portion of the insulatedtank 240 via warm water return line 276. This secondary heat exchangerloop can be switched in and out of the system by valves 288 as necessarywhen instantaneous cooling load is needed. Additionally, a secondarycooling source (not shown), such as an external cold water line or thelike, may be placed in thermal contact with the refrigerant in thesecondary heat exchanger to additionally boost the pre-cooling of therefrigerant entering the primary heat exchanger 260 or the URMV 246.

FIG. 3 illustrates an embodiment of a refrigerant-based thermal energystorage and cooling system with multiple enhanced heat exchangercapability. Similarly, as is detailed above in the previous Figures, athermal energy storage and cooling system with a conventional condensingunit 302 (air conditioner) utilizes a compressor and condenser toproduce high-pressure liquid refrigerant delivered through ahigh-pressure liquid supply line to the refrigeration management anddistribution system 304 which can include a universal refrigerantmanagement vessel 346 and a liquid refrigerant pump 320. A mixed-phaseflow regulator (not shown) may be used to receive high-pressure liquidrefrigerant from the high-pressure liquid supply line and regulate theflow of refrigerant fed from the compressor to the heat load.Low-pressure mixed-phase refrigerant is accumulated in a universalrefrigerant management vessel 346 that separates the liquid phase fromthe vapor phase refrigerant.

In thermal energy storage mode, the universal refrigerant managementvessel 346 feeds liquid refrigerant through a liquid line feed to theprimary heat exchanger 360 that stores the cooling in the form of ice oran ice block 342. Upon delivering the cooling to the primary heatexchanger 360, mixed-phase refrigerant is returned to the universalrefrigerant management vessel 346 via a wet suction return line 324. Adry suction return line returns vapor phase refrigerant to be compressedand condensed in the condensing unit 302 to complete the thermal energystorage cycle.

In cooling mode, the universal refrigerant management vessel 346 feedsliquid refrigerant to a liquid refrigerant pump 320, which then pumpsthe refrigerant to an evaporator coil 322. Upon delivering the coolingto the evaporator coil 322, mixed-phase refrigerant is returned to theprimary heat exchanger 360 and cooled utilizing an ice block 342 that ismade during thermal energy storage mode. The vapor phase refrigerant iscondensed into liquid by the ice cooling, and returned to the universalrefrigerant management vessel 346 via liquid feed line 366. A secondaryheat exchanger unit 370 and a tertiary heat exchanger unit 390 introducean external melt to the system to provide additional instantaneouscooling load to the system.

By providing a system with internal/external melt capability, thermalenergy stored in the form of an ice block 342 is melted internally byfreezing/discharging coils within the primary heat exchanger 360 andexternally by circulating cold water from the periphery of the blockthrough the secondary and tertiary heat exchangers 370 and 390. Thisallows the system to react to very large instantaneous cooling demands.Additional heat exchange units can be added to the system in the mannerof tertiary heat exchanger 390 to regulate a wide variety of coolingload demands. During this second time period (cooling mode), warm vaporphase refrigerant circulates through ice freezing/discharging coilswithin the primary heat exchanger 360 and melts the ice block 342 fromthe inside out providing a refrigerant condensing function.

Water at the bottom of the insulated tank 340 is drawn into cold waterline 374 by a water pump 372 and fed to the secondary and tertiary heatexchangers 370 and 390. Refrigerant, returning from the evaporator coil322 can be diverted from its normal path of the wet suction return 324and fed to the secondary and tertiary heat exchangers 370 and 390 viasecondary cooling inlet line 378. Here, the warm refrigerant is cooledby water entering from cold water line 374 and condenses, increasing theproportion of liquid in the refrigerant which is then fed through asecondary cooling outlet line 380 to the primary heat exchanger 360where the header configuration drives most of the liquid to theuniversal refrigerant management vessel 346 and the vapor to the primaryheat exchanger 360. This remaining refrigerant vapor is then condensedwithin the primary heat exchanger 360 in the insulated tank 340. Aftertransferring heat to the refrigerant in the secondary and tertiary heatexchangers 370 and 390, the warmed water is returned to the upperportion of the insulated tank 340 via warm water return line 376. Thesesecondary and tertiary heat exchanger loops can be switched in and outof the system by valves 388 as necessary when instantaneous cooling loadis needed. A plurality of additional heat exchangers can be added to thesystem in a similar manner to the tertiary heat exchanger in series orparallel to accomplish additional enthalpy reduction of the refrigerantif needed.

FIG. 4 illustrates an embodiment of a refrigerant-based thermal energystorage cooling system with enhanced heat exchange capability utilizinga shared fluid bath. A thermal energy storage and cooling system with aconventional condensing unit 402 (air conditioner) utilizes a compressorand condenser to produce high-pressure liquid refrigerant deliveredthrough a high-pressure liquid supply line 412 to the refrigerationmanagement and distribution system 404 which can include a universalrefrigerant management vessel 446 and a liquid refrigerant pump 420. Theuniversal refrigerant management vessel 446 receives the low-pressuremixed phase 462 liquid refrigerant that has been dropped in pressurefrom the high-pressure liquid supply line 412. Refrigerant isaccumulated in the universal refrigerant management vessel 446 thatseparates the liquid-phase refrigerant from the vapor-phase refrigerant.Low-pressure mixed-phase refrigerant 462 is accumulated in a universalrefrigerant management vessel 446 that separates the liquid-phaserefrigerant from the vapor-phase refrigerant. A mixed-phase regulator(not shown) can be used to minimize vapor feed to the universalrefrigerant management vessel 446 from the compressor, while decreasingthe refrigerant pressure difference from the condenser to the evaporatorsaturation pressure.

In thermal energy storage mode, the universal refrigerant managementvessel 446 feeds liquid refrigerant through liquid feed line 466 to theprimary heat exchanger 460 that stores the cooling (thermal energy) inthe form of ice or an ice block 442. Upon delivering the cooling to theprimary heat exchanger 460, mixed-phase refrigerant is returned to theuniversal refrigerant management vessel 446 via a wet suction returnline 424. Dry suction return line 418 returns vapor phase refrigerant tobe compressed and condensed in the condensing unit 402 to complete thethermal energy storage cycle.

In cooling mode, the universal refrigerant management vessel 446 feedsliquid refrigerant through pump inlet line 464 to a liquid refrigerantpump 420 which then pumps the refrigerant to an evaporator coil 422 viapump outlet line 460. Upon delivering the cooling to the evaporator coil422, mixed-phase or saturated refrigerant is returned to the primaryheat exchanger 460 via a low-pressure vapor line 468 and is condensedand cooled utilizing an ice block 442 that is made during thermal energystorage mode. The vapor-phase refrigerant is then returned to theuniversal refrigerant management vessel 446 via liquid feed line 466. Asecondary heat exchanger unit 470, located within the fluid 443 that iscontained inside of the insulated tank 440 but outside of the ice block442, may be used to introduce an external melt and provide additionalinstantaneous cooling load to the system in a serial configuration. Byproviding a system with internal/external melt capability, thermalenergy stored in the form of an ice block 442 is melted internally byfreezing/discharging coils within the primary heat exchanger 460 andexternally by circulating/and or contacting fluid from the periphery ofthe block with the secondary heat exchanger 470. This allows the systemto realize increased instantaneous cooling capacity in a simple and selfcontained manner. An additional circulating pump or air pump may beutilized to destratify and mix the fluid within the chamber.

During this second time period (cooling mode), warm vapor phaserefrigerant circulates through ice freezing/discharging coils within theprimary heat exchanger 460 and melts the ice block 442 from the insideout, providing a refrigerant condensing function. As heat is transferredfrom these ice freezing/discharging coils to the surrounding ice block442, a layer of water forms around the annulus of the individual coils.As described above, once this layer of water forms a sufficient envelopearound a coil, it begins to act as an insulator between the icefreezing/discharging coils and the ice block 442. This condition willpersist until such a time when the water annulus becomes large enoughfor considerable water circulation to overcome this localized thermalstratification. In order to compensate for the inability of the systemto produce high levels of instantaneous cooling load, the outer surfaceof the ice block is additionally utilized.

Within the insulated tank 440, the entirety of the water is not frozenduring the ice build cycle, and therefore, an amount of watercontinuously surrounds the block of ice. At the bottom of the insulatedtank 440, this water is very near the freezing point (approximately33-34° F.), and is used to contact the secondary heat exchanger 470located within the fluid 443. Refrigerant, returning from the evaporatorcoil 422 can be diverted from its normal path of the wet suction return424 and fed to the secondary heat exchanger 470 via secondary coolinginlet line 480. Here, the warm refrigerant is cooled by watersurrounding the ice block 442 and condenses, increasing the proportionof liquid in the refrigerant which is then fed through a secondarycooling outlet line 480 to the primary heat exchanger 460 where theheader configuration drives most of the liquid to the universalrefrigerant management vessel 446 and the vapor to the primary heatexchanger 460. This remaining refrigerant vapor is then condensed withinthe primary heat exchanger 460 in the insulated tank 440. Aftertransferring heat to the refrigerant in the secondary heat exchanger470, the warmed water is circulated and mixed within the insulated tank440. This secondary heat exchanger loop can be switched in and out ofthe system by valves 488 as necessary when instantaneous cooling load isneeded.

FIG. 5 illustrates an embodiment of a refrigerant-based thermal energystorage cooling system with enhanced heat exchange capability utilizinga shared fluid bath. A thermal energy storage and cooling system with aconventional condensing unit 502 (air conditioner) utilizes a compressorand condenser to produce high-pressure liquid refrigerant deliveredthrough a high-pressure liquid supply line 512 to the refrigerationmanagement and distribution system 504 which can include a universalrefrigerant management vessel 546 and a liquid refrigerant pump 520. Theuniversal refrigerant management vessel 546 receives the low-pressuremixed phase 562 liquid refrigerant that has been dropped in pressurefrom the high-pressure liquid supply line 512. Refrigerant isaccumulated in the universal refrigerant management vessel 546 thatseparates the liquid-phase refrigerant from the vapor-phase refrigerant.Low-pressure mixed-phase refrigerant 562 is accumulated in a universalrefrigerant management vessel 546 that separates the liquid-phaserefrigerant from the vapor-phase refrigerant. A mixed-phase regulator(not shown) can be used to minimize vapor feed to the universalrefrigerant management vessel 546 from the compressor, while decreasingthe refrigerant pressure difference from the condenser to the evaporatorsaturation pressure.

In thermal energy storage mode, the universal refrigerant managementvessel 546 feeds liquid refrigerant through liquid feed line 566 to theprimary heat exchanger 560 that stores the cooling (thermal energy) inthe form of ice or an ice block 542. Upon delivering the cooling to theprimary heat exchanger 560, mixed-phase refrigerant is returned to theuniversal refrigerant management vessel 546 via a wet suction returnline 524. Dry suction return line 518 returns vapor phase refrigerant tobe compressed and condensed in the condensing unit 502 to complete thethermal energy storage cycle.

In cooling mode, the universal refrigerant management vessel 546 feedsliquid refrigerant through pump inlet line 564 to a liquid refrigerantpump 520 which then pumps the refrigerant to an evaporator coil 522 viapump outlet line 560. Upon delivering the cooling to the evaporator coil522, mixed-phase or saturated refrigerant is returned to the primaryheat exchanger 560 via a low-pressure vapor line 568 and is condensedand cooled utilizing an ice block 542 that is made during thermal energystorage mode. The vapor-phase refrigerant is then returned to theuniversal refrigerant management vessel 546 via liquid feed line 566. Asecondary heat exchanger unit 570, located within the fluid 543 that iscontained inside of the insulated tank 540 but outside of the ice block542, may be used to introduce an external melt and provide additionalinstantaneous cooling load to the system in a parallel configuration. Byproviding a system with simultaneous internal and external meltcapability, thermal energy stored in the form of an ice block 542 ismelted internally by freezing/discharging coils within the primary heatexchanger 560 and externally by circulating/and or contacting fluid fromthe periphery of the block with the secondary heat exchanger 570. Thisallows the system to realize increased instantaneous cooling capacity ina simple and self contained manner. An additional circulating pump orair pump may be utilized to destratify and mix the fluid within thechamber.

During this second time period (cooling mode), warm vapor phaserefrigerant circulates through ice freezing/discharging coils within theprimary heat exchanger 560 and melts the ice block 542 from the insideout, providing a refrigerant condensing function. As heat is transferredfrom these ice freezing/discharging coils to the surrounding ice block542, a layer of water forms around the annulus of the individual coils.As described above, once this layer of water forms a sufficient envelopearound a coil, it begins to act as an insulator between the icefreezing/discharging coils and the ice block 542. This condition willpersist until such a time when the water annulus becomes large enoughfor considerable water circulation to overcome this localized thermalstratification. In order to compensate for the inability of the systemto produce high levels of instantaneous cooling load, the outer surfaceof the ice block is additionally utilized.

Within the insulated tank 540, the entirety of the water is not frozenduring the ice build cycle, and therefore, an amount of watercontinuously surrounds the block of ice. At the bottom of the insulatedtank 540, this water is very near the freezing point, and is used tocontact the secondary heat exchanger 570 located within the fluid 543.Refrigerant, returning from the evaporator coil 522 can be diverted fromits normal path of the wet suction return 524 and fed simultaneously tothe secondary heat exchanger 570 and the primary heat exchanger 560 viasecondary cooling inlet line 580. Here, the warm refrigerant is cooledby water surrounding the ice block 542 by secondary heat exchanger 570and the primary heat exchanger 560 within the ice block 542 andcondenses. The header configuration then drives most of the liquid tothe universal refrigerant management vessel 546 and the vapor to theprimary heat exchanger 560 and the secondary heat exchanger 570.Remaining refrigerant vapor is eventually condensed within the primaryheat exchanger 560 in the insulated tank 540. After transferring heat tothe refrigerant in the secondary heat exchanger 570, the warmed water iscirculated and mixed within the insulated tank 540. This secondary heatexchanger loop can be switched in and out of the system by valve 590 asnecessary when instantaneous cooling load is needed.

Conventional thermal energy storage units that utilize arefrigerant-based, internal melt, ice on coil system, are constrained bya cooling load capacity that is limited by the heat transfer coefficientof the ice melt. In such a system, a condensing unit is used to storerefrigerant energy during one time period in the form of ice (icebuild), and provide cooling from the stored ice energy during a secondtime period (ice melt). This melt process typically starts on theoutside of a heat transfer tube of a heat exchanger that is imbeddedwithin the block of ice, through which warm refrigerant flows. As heatis transferred through the heat exchanger to the ice, an annulus ofwater forms between the tubes and the ice, and in the absence ofcirculation, acts as an insulator to further heat transfer. Thus, thecapacity of the heat exchanger is limited in the early stages of themelt prior to a time when a large enough water annulus allows mixing ofthe water in the area of the ice block. Previous attempts to improveheat transfer between a heat transfer tube that is surrounded by icehave involved creating turbulence by bubbling air in the jacket ofwater. This method is limited by poor efficiency, reliability and highcost (both energy and dollars).

The present invention overcomes the disadvantages and limitations of theprior art by providing a method and device to increase the cooling loadthat can be provided by a refrigerant-based thermal energy storage andcooling system with an improved arrangement of heat exchangers. This isaccomplished by circulating cold water surrounding a block of ice, usedas the thermal energy storage medium, through a secondary heat exchangerwhere it condenses refrigerant vapor returning from a load. Therefrigerant is then circulated through a primary heat exchanger withinthe block of ice where it is further cooled and condensed. This systemis known as an internal/external melt system because the thermal energy,stored in the form of ice, is melted internally by a primary heatexchanger and externally by circulating cold water from the periphery ofthe block through a secondary heat exchanger.

In a typical ice storage unit, the water in the tank that surrounds theperiphery of the ice never freezes solid. This water remainsapproximately 32° F. at the bottom of the tank for nearly the entiretyof the melt period. By circulating this water through a secondary heatexchanger and then back into the tank with a small circulation pump,greater heat exchange efficiencies can be realized. The secondary heatexchanger is a high-efficiency heat exchanger such as a coaxialcondenser or a brazed plate heat exchanger or the like and is used tolower the enthalpy (lower the temperature and/or condense) therefrigerant prior to entering the main heat exchanger in the ice tank.As a result, the total cooling capacity of the system is now the sum ofthe capacities provided by the two heat exchangers. By using as many ofthe secondary heat exchangers as needed, the system can provide theflexibility to match the ice storage system to the requirement of thecooling load.

The detailed embodiments detailed above, minimize additional componentsand use very little energy beyond that used by the condensing unit tostore the thermal energy. The refrigerant energy storage design has beenengineered to provide flexibility so that it is practicable for avariety of applications. The embodiments can utilize stored energy toprovide chilled water for large commercial applications or providedirect refrigerant air conditioning to multiple evaporators. The designincorporates multiple operating modes, the ability to add optionalcomponents, and the integration of smart controls that guarantee energyis stored at maximum efficiency. When connected to a condensing unit,the system stores refrigeration energy in a first time period, andutilizes the stored energy during a second time period to providecooling. In addition, both the condensing unit and the refrigerantenergy storage system can operate simultaneously to provide coolingduring a third time period.

Numerous advantages are realized in utilizing additional heat exchangerloops to manage coolant in high-efficiency thermal energy storage andcooling systems. The embodiments described can increase the coolingcapacity of the system by as much as 400% to match the cooling loadrequired. The system eliminates complicated and expensive airdistribution systems that are subject to great reliability concerns andthe system can readily adapt to buildings cooled by cold-waterdistribution. These embodiments have widespread application in allcooling systems, extending beyond applications for air-conditioning. Forinstance, this method can be used for cooling any fluid medium using icestorage. Combined with an efficient method of making ice, theseembodiments can have wide application in dairy, and petroleumindustries.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andother modifications and variations may be possible in light of the aboveteachings. The embodiment was chosen and described in order to bestexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the inventionin various embodiments and various modifications as are suited to theparticular use contemplated. It is intended that the appended claims beconstrued to include other alternative embodiments of the inventionexcept insofar as limited by the prior art.

What is claimed is:
 1. A thermal energy storage and cooling systemcomprising: an air conditioning system having a mechanical compressorthat operates in a closed loop refrigeration circuit; at least onethermal energy storage tank; a liquid medium that transfers heat to andfrom said at least one thermal storage energy tank; at least one heatexchanger that transfers heat from said liquid medium to said closedloop refrigeration circuit; a pump that circulates said liquid medium;and, a controller that regulates the flow of said liquid medium to saidclosed loop refrigeration circuit to enable heat to be transferred tosaid at least one thermal storage tank without said air conditionercompressor in operation.
 2. The thermal energy storage and coolingsystem of claim 1 further comprising: at least one valve that starts,stops and regulates the flow of heat from said air conditioning systemto and from said thermal storage tank, said valve allowing heat to betransferred by said air conditioning system as if said thermal energytransfer unit and said thermal storage tank were not present in saidsystem.
 3. The thermal energy storage and cooling system of claim 2further comprising: a plurality of said thermal energy transfer unitsused in association with a plurality of said air conditioning systemsthat transfer heat to or from one or more shared said thermal energystorage tanks.